Mass. police converge on Watertown

Officials work a crime scene in Watertown, Mass., Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)

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Officials secure an area in Watertown, Mass., Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)

AP

A vehicle carrying officers in tactical gear arrives at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)

AP

Officers wearing tactical gear arrive at the Watertown neighborhood of Boston, Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)

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An armored vehicle arrives in Watertown, Mass., early Friday, April 19, 2013. Reports of explosives being detonated and police are telling reporters to turn off their cell phones. Dozens of officers and National Guard members are in Watertown, where television outlets report that gunfire and explosions have been heard. (AP Photo/Julio Cortez)

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Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)

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A bomb squad truck arrives at an incident Friday, April 19, 2013, in Watertown, Mass. in which shots were reported to have been fired. (AP Photo/Craig Ruttle)

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A Police official looks over object that was picked up by a remote control device, left, as they investigate an incident in Friday, April 19, 2013, in Watertown, Mass. in which shots were reported to have been fired. (AP Photo/Craig Ruttle)

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Heavily armed officers arrive during the investigation of an incident Friday, April 19, 2013, in Watertown, Mass. in which shots were reported to have been fired. (AP Photo/Craig Ruttle)

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A police official looks over an object that was picked up by a remote control device, left, as they investigate an incident Friday, April 19, 2013, in Watertown, Mass. in which shots were reported to have been fired. (AP Photo/Craig Ruttle)

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Police officers work a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)

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This surveillance photo released via Twitter Friday, April 19, 2013 by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP Photo/Boston Police Department)

Boston Police Department

Officials brief the media on a standoff in Watertown, Mass., Friday, April 19, 2013. Authorities say one of two suspects in the Boston Marathon bombing is dead and a massive manhunt is underway for another in the Boston suburb of Watertown early Friday morning April 19, 2013. (AP Photo/Julio Cortez)

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Police officers walk near a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)

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Police officers stand ready at a crime scene Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke)

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Officials address the media during a news conference in Watertown, Mass., Friday, April 19, 2013. Officials are urging residents of Watertown and surrounding towns to stay indoors. One of two suspects in the Boston Marathon bombing is dead after the killing of a university officer and a shootout with police, and a massive manhunt is underway for the other, authorities said early Friday. (AP Photo/Julio Cortez)

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Police hold a man in handcuffs, who they later released, in a neighborhood of Watertown, Mass., Friday, April 19, 2013. Much of the town is blocked as police and federal officers hunt for suspects in the Boston Marathon explosions. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)

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A police officers rides on the back of a van at a staging area as a manhunt is conducted for a suspect Friday, April 19, 2013, in Watertown, Mass. One of two suspects in the Boston Marathon bombing is dead and a massive manhunt is underway for another, authorities said early Friday April 19, 2013. Residents of Watertown, a Boston suburb, have been advised to keep their doors locked and not let anyone in. (AP Photo/Matt Rourke)

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Kurt Schwartz, director of the Massachusetts Emergency Management Agency, addresses the media in Watertown, Mass., Friday, April 19, 2013. Officials are urging residents of Watertown and surrounding towns to stay indoors as manhunt for a suspect is ongoing. (AP Photo/Julio Cortez)

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A Department of Homeland Security officer, right, prepares to enter an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)$RETURN$$RETURN$

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With his weapon drawn, an official inspects an apartment building in Watertown, Mass., Friday, April 19, 2013. Dozens of officers and National Guard members are in Watertown, where gunfire and explosions were heard early Friday morning. (AP Photo/Julio Cortez)

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A woman looks out a window at her home as police start to search an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday, authorities said as the manhunt intensified for a young man described as a dangerous terrorist. (AP Photo/Charles Krupa)$RETURN$$RETURN$

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Police in tactical gear arrive on an armored police vehicle as they surround an apartment building while looking for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)

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Officials inspect vehicles in Watertown, Mass., Friday, April 19, 2013. Dozens of officers and National Guard members are in Watertown, where gunfire and explosions were heard early Friday morning. (AP Photo/Julio Cortez)

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With his weapon drawn, an officer inspects dumpsters behind an apartment building in Watertown, Mass., Friday, April 19, 2013. Dozens of officers and National Guard members are in Watertown, where gunfire and explosions were heard early Friday morning. (AP Photo/Julio Cortez)

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Residents look out a window as officials inspect an apartment building in Watertown, Mass., Friday, April 19, 2013. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during their getaway attempt in a long night of violence that left one of them dead and another still at large Friday. (AP Photo/Julio Cortez)

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Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)

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A police officer in tactical gear conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)

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A police officer enters an apartment building with his dog while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)

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Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)

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Residents view police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Matt Rourke)

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Police walk through a neighborhood in Watertown, Mass., while searching for a suspect in the Boston Marathon bombings, Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)

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A police official inspects an object that was picked up by a remote control device, left, following a shootout with suspects in the Boston Marathon bombings early Friday, April 19, 2013, in Watertown, Mass. (AP Photo/Craig Ruttle)

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Information is seen on a computer inside a Boston Police vehicle as officials searched an apartment building in Watertown, Mass., Friday, April 19, 2013. Dozens of officers and National Guard members are in Watertown, where gunfire and explosions were heard early Friday morning. All residents of Boston were ordered to stay in their homes, as the search for the surviving suspect in the marathon bombings continued after a long night of violence that left another suspect dead. (AP Photo/Julio Cortez)

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Police patrol through a neighborhood in Watertown, Mass., while searching for a suspect in the Boston Marathon bombings, Friday, April 19, 2013. The bombs that blew up seconds apart near the finish line of the Boston Marathon left the streets spattered with blood and glass, and gaping questions of who chose to attack and why. (AP Photo/Charles Krupa)

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Police patrol through a neighborhood in Watertown, Mass., while searching for a suspect in the Boston Marathon bombings, Friday, April 19, 2013. All residents of Boston were ordered to stay in their homes Friday morning as the search for the surviving suspect in the marathon bombings continued after a long night of violence that left another suspect dead. (AP Photo/Charles Krupa)